1. What is a Tankless Water Heater Sizing Calculator?

Definition: This calculator determines the required flow rate (GPM) for a tankless water heater by summing the flow rates of all potential simultaneously used fixtures.

Purpose: It helps homeowners and plumbers properly size a tankless water heater to meet household hot water demands.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( GPM \) — Gallons per minute required for the tankless water heater
• \( \sum Fixture\,GPM \) — Sum of flow rates from all fixtures that might run simultaneously

Explanation: The calculator adds up the flow rates of showers, sinks, dishwashers, and washing machines that could be used at the same time.

3. Importance of Proper Sizing

Details: Correct sizing ensures adequate hot water supply during peak usage while avoiding oversized units that waste energy.

4. Using the Calculator

Tips: Enter the flow rate for each fixture (default values provided). Consider your household's peak usage patterns when determining which fixtures to include.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical flow rate for fixtures?
A: Standard flow rates: Shower (2.5 GPM), Sink (1.5 GPM), Dishwasher (1.0 GPM), Washer (2.0 GPM).

Q2: Should I include all fixtures in my home?
A: Only include fixtures that might run simultaneously during peak usage times.

Q3: What if I have low-flow fixtures?
A: Adjust the input values accordingly (e.g., low-flow showerheads might be 1.5-2.0 GPM).

Q4: How does temperature rise affect sizing?
A: This calculator determines flow rate needs. Temperature rise (based on groundwater temp) affects the heater's BTU requirements.

Q5: Should I add a safety margin?
A: It's recommended to add 10-20% to the calculated GPM for comfort and future needs.